The present invention relates to a stereo image measuring device and, more particularly, to a device for measuring a three-dimensional image from a stereo image. Throughout the specification, “off-line measurement” means executions of image photographing, for example, at a measuring site, and of operations other than the photographing at a different calculation and analyzing site. On the other hand, “on-line measurement” means executions of image measuring, and also of displaying of a three-dimensional image, for example, at a measuring site.
In the conventional art of digital photogrammetry, three-dimensional measurement and analysis from an obtained digital image have been carried out in the following manner. First, orientation is carried out based on several imprinted control points to provide stereoscopic vision. Then, stereo matching is carried out from a plurality of obtained images to calculate a three-dimensional coordinate, and thus a three-dimensional image is analyzed. In the stereo matching in particular, a coarse-to-fine image correlation processing method or the like is used in order to surely obtain three-dimensional data. Here, according to the coarse-to-fine image correlation processing method, correlation processing is carried out in stages gradually from a low-resolution image to a high-resolution image, rather than executing correlation processing among high-resolution images from the beginning. This method reduces the number of local errors, thereby enhancing reliability (see Image Analysis Handbook, p. 709, compiled under the supervision of M. Takagi, and Y. Shimoda). The three-dimensional measurement has also been carried out by utilizing a survey instrument such as a total station, a GPS or the like.
In addition, to measure a relatively large object in the form of a three-dimensional image in the conventional art, the points of measurement have been scanned by use of the survey instrument such as a total station, or the points of measurement have been increased by moving the GPS, and thus the three-dimensional image has been displayed by a collection of a number of small surfaces surrounded with the plurality of points of measurement. Another method has also been available, that is, three-dimensional measurement has been carried out by executing image correlation processing (stereo matching) or the like from a photographed stereo image, and then displaying a three-dimensional image as a collection of a number of surface shapes.